Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uflorida!unf7!tlvx!sysop
From: sysop@tlvx.UUCP (SysOp)
Newsgroups: comp.sys.amiga
Subject: Re: Multifinder - Just the Facts, man.
Summary: argh, multitasking terminology
Keywords: Macs, uh-oh
Message-ID: <304@tlvx.UUCP>
Date: 4 May 90 01:06:42 GMT
References: <20499@boulder.Colorado.EDU> <8930@hubcap.clemson.edu> <10143@sdcc6.ucsd.edu>
Organization: Temporal Vortex BBS of Jacksonville, Florida
Lines: 69

In article <10143@sdcc6.ucsd.edu>, cs163wed@sdcc10.ucsd.edu (see far) writes:
> In article <8930@hubcap.clemson.edu> chrise@hubcap.clemson.edu (Chris Everhart) writes:
> >In article <20499@boulder.Colorado.EDU>, judd@boulder.Colorado.EDU (Steve Judd) writes:
> >> 
> >> Posting the second...
> >There is indeed a catch.  I have used the multifinder (on AMAX) before, and
> >find it to be quite lame.  It requires incredible amounts of memory and does
> >not alow preemtive multitasking.  In fact, I wouldn't call what it does
> >multitasking at all.  If you are running a word processor and something to
> >do calculations for you, the computer will quit running the calculations
> >program while you are using the word processor.  This isn't multitasking at
> >all.  (if I'm wrong, someone correct me)  I call it program swapping.  The
> >processor doesn't appear to be cycling time between the tasks.  This kind of
> >multitasking is the what people think of when they say "who needs it?"  The
> >Amiga is capable of running several programs SIMULTANEOUSLY.  I can have my

From what I've heard about multi-finder (very little), perhaps the word
processor was poorly-written in some area.  It should have occasionally
relinquished control.  (Inbetween keystrokes, one would think!  Geesh!)

> 
> ISn't the AMiga's multi-tasking program swapping?   Unless you have

Argh, no, he was talking about something different!  When he meant program
swapping, he meant that when he started using the word processor, the other
program stopped dead, and waited until he went back, even if that were 
MINUTES later!  There was no appearance of running simultaneously with
the situation he mentioned.  There have been programs for various machines
that, for instance, swap the contents of memory to disk, then load another
program that was saved in progress, and resumed execution.  I would call
that "program swapping".

> several amigas at once, you can never run programs simultaneously.
> Amiga's multitasking only tricks you into thinking it is running
> programs "simultaneously". 

This is what people mean by "multi-tasking."

The Amiga multitasking is "preemptive" in that (ok I'm going to simplify
this terribly) a program only gets a small amount of time, then it's
removed from the CPU, and the next program in the ready queue is run, but
only for a short while.  The program itself doesn't know when it'll be
kicked off the CPU, but since it's environment is saved and restored,
it doesn't have to know.  Each duration is small, so on the whole, it
looks like they're all running simultaneously.

(BTW, Transactor had a programs for the C-64 that both "program swapped"
and "multitasked" BASIC programs.  Heh.  Not too useful, but cute.)

Another way to multi-task is to allow the program to take the CPU for
as long as it wants, and only let other programs have the CPU whenever
they're done.  So, things seem to multi-task when all programs are nice,
and when one isn't nice, it hogs it all.  Meanwhile, it would be hard to
judge just how much time each program gets; do they get a fair amount?
Anyway, programs will appear to run simultaneously so long as one (or
more) programs aren't real hogs.

> 
> After all, you get only one 68000 in an amiga, don't you?

Then explain why other OS's running on other one-CPU machines use the term
"multi-tasking"?  :-)


> >
> >Chris Everhart
> >chrise@hubcap.clemson.edu
> 
...